Under various wireless communications standards, a transmission from a mobile wireless device to an access point (AP) may be performed in two distinct modes: 1) While operating in a polled mode, a mobile wireless device may transmit to the AP only when it is specifically polled by the AP to do so. This technique may be used to keep two or more mobile wireless devices from trying to transmit to the AP at the same time and thereby causing a “collision” of their signals that might make both of their transmissions unintelligible. However, the overhead burden on the AP of separately polling every device may reduce the potential throughput of the network. 2) While operating in a medium contention (MC) mode, a mobile wireless device may transmit to the AP without being polled. While avoiding the AP's overhead burden of separately polling each device, this technique may result in collisions and subsequent retransmissions, which can also reduce network throughput. However, the mobile wireless devices that are contending for the medium in this manner may use other techniques to reduce the likelihood of collisions. One such technique for doing so is called Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA), in which each mobile wireless device may transmit only after determining that the channel is not already being used. Since two or more devices may detect an unused channel at the same time and then try to transmit at the same time, this technique may still result in collisions, followed by retransmissions until all the packets are successfully transmitted.
One method of managing the medium contention mode is by having the AP or other node issue packets that reserve the medium (i.e., the packets direct the mobile wireless devices to refrain from initiating a communications sequence for a period of time, thereby reserving the channel for those devices that are specifically requested to use it). This process may become more complicated when a network has some mobile wireless devices that follow newer, higher-throughput standards, and also has some less capable mobile wireless devices that follow older standards. If the less capable devices have difficulty recognizing the communications with the more capable devices, the less capable devices may not recognize a directive to refrain from using the channel. Modifying the mobile wireless devices to manage this problem for themselves may place an unacceptable performance burden on those devices, especially on the older, slower, and/or less capable mobile wireless devices.